1. Field of the Invention
This invention relates to methods and apparatus for shaping materials, suitably materials for use in the building or furnishing industries.
2. Prior Art
In the building industry, many items conventionally made from wood, plaster, etc. are now made from plastics materials. Particularly important amongst these plastics materials are foamed plastics products, which are used as replacements for wood in the manufacture of doors and window surrounds and for plaster in the manufacture of ceiling tiles, cornices, etc.
Amongst the widely used foamed products are polystyrene and polyurethane foams, though these have the disadvantage of being combustible. Even when modified with flame retardants, they give off noxious poisonous fumes or dense smoke when exposed to flame and are a serious hazard in fire. For these reasons, there is a growing prejudice against their use, especially in private dwellings.
Foamed phenolic resins have also been available for many years and can be formulated so as not to support flame and to have a lower tendency than polystyrene or polyurethane foams to generate toxic fumes in the presence of flame. The basic material, i.e. the phenolic resin, is also relatively cheap. Nevertheless, hitherto they have not gained as wide acceptance in industry as polyurethane inter alia because of their generally poor physical strength; they tend to be brittle and friable and easily crushed. Further, while they can be manufactured as simple shapes such as slabs and blocks, they cannot readily be moulded to produce complex shapes. One reason for this is that their poor strength can create difficulties in removing the article from the mould. Thus, more complex shapes have to be produced from slabs or blocks by a further operation such as machining.
EP-A-0.010.353 discloses a method of forming a foamed phenolic resin composition by causing or allowing a mixture of phenolic resole, acid hardener and finely divided particulate solid to cure under conditions in which foaming of the mixture is caused primarily or solely by volatilisation of small molecules present in the resole or formed as a by-product of the curing reaction. The formation of such foams is described in detail in EP-A-0.101.353 and foamed bodies comprising these foams are obtainable as "ACELL" from Company `A` Foam Limited of Addison Road, Chesham, Buckinghamshire, England. Preferably, the foam has a density in the range 100 to 500 kg/m.sup.3, more preferably 150 to 400 kg/m.sup.3 and most preferably 150 to 250 kg/m.sup.3.
Foam produced by the method disclosed in EP-A-0.101.353 can have a fine texture of substantially uniform pore size, excellent fire resistance, high thermal insulation and good resistance to heat.
With conventional materials such as plaster mixes and the newer foamed plastics materials, considerable expense is incurred in producing desired decorative finishes on ceiling tiles, panels, etc. and in producing desired profiles for cornices, door moldings, etc. This is true whether the desired finish or profile is produced by casting in a suitable mould or by machining or stamping a moulded product.
It is therefore an object of the present invention to provide a method of shaping materials, suitably materials for use in the building or furnishing industry, which can be carried out quickly and cheaply and which readily allows a change from one profile to another to be effected during manufacture.